Often overlooked, but always riveting (at least for me), Howard holds a special place among Brit actors; the following is from a good piece at Bright Lights by Imogen Smith:

Summed up by David Thomson as “a candid, scathing personality,” Howard wasn’t charming like his namesake Leslie; he wasn’t suave and sinister like James Mason or George Sanders; he wasn’t romantic like Olivier or creepy like Eric Portman; he wasn’t a matinee idol like Dirk Bogarde or a rough-hewn working man like Stanley Baker. He didn’t fit any of the standard types of the Englishman, as understood by Hollywood: charming gent, arrogant aristocrat, prattling Cockney. But he was utterly British in his impatient rigor, that dry, sharp, scathing quality.

[…]

That he came on the scene just as Britain was emerging from World War II was a piece of good luck. The skeptical, burned-out mood of the time brought him ideal roles, parts that explored the point at which his stiff upper lip met something unpleasantly hard-edged, at which his bulldog Britishness became bullying, and his scorn turned corrosive and doubled-edged.

On Howard in The Third Man:

Pushing Major Calloway to the side, as just another character rather than the central observer, gives the film its ambiguity. His strict, impatient moral clarity is not privileged as the only reasonable response to the situation. Instead, while ultimately vindicated, he also appears condescending, callous, and occasionally petty (he is nettled by Martins’ sly insistence on calling him Callahan, snapping, “I’m English, not Irish.”) Sporting a military beret and neatly trimmed mustache that accent the chiseled lines of his face, speaking in a clipped undertone, Howard is the aesthetic opposite of Orson Welles with his fleshy, swarthy handsomeness; his rich, mesmeric voice; his feline smile and elegant black overcoat. Welles as Lime is the personification of bombed-out Vienna: both demonstrate the allure of ruins, of physical and moral corruption.

I recommend They Made Me a Fugitive (a really good British noir, as Smith says), Green for Danger, The Third Man (of course — has anyone NOT seen it?), Outcast of the Islands, Run for the Sun (a remake of The Most Dangerous Game with Richard Widmark & Jane Greer which I found a lot of fun), Windwalker, & the 1962 version of Mutiny on the Bounty with Brando.

I’ve heard good things about The Clouded Yellow & So Well Remembered too.